A conventional electrical switching contactor includes an "E"-shaped iron motor section, a motor coil on a spool having a center mounted over the middle leg of the motor section, and an armature shaped with three contact surfaces which mate with the ends of the three legs of the "E"-shaped iron motor section. The armature is movably supported with respect to the motor section so that, in response to a current being applied to the motor coil, an electro-magnetic field can draw, against a biasing separation force, the armature into contact with the motor section. By mounting one or more contacts on the armature and arranging a corresponding set of fixed contacts in proper relationship to the armature-mounted contacts, the control current applied to the motor coil is used in response to power applied to switch "on" or "off" electrical loads in series with contacts.
Known contactors have been manufactured by individually laminating or stamping out iron cores for the respective "E"-shaped motor section and armature. The coil-spool combination is separately assembled and subsequently placed over the center leg of the "E"-shaped motor section. While slight improvements have been made from time to time to increase the efficiencies and strengths associated with the electro-magnetic force which pulls the armature toward the motor section in the above method of manufacture, the magnitude of the electro-magnetic pulling force for a given application is largely dependent upon size of the laminated core and power applied to the coil. An application requiring a relatively small electromagnetic pulling force requires a relatively small contactor, and an application requiring a relatively large electro-magnetic pulling force requires a relatively large contactor.
The foregoing assembling technique suffers from several drawbacks. One drawback is that the foregoing assembly technique may lead to a loss of magnetic core permeability due to assembly interface air gaps, eddy currents, opposing material grain directions and stresses in the stamped core laminations. These deficiencies, in turn, produce relatively large variabilities. Another drawback is that core laminations in the assembly technique use an involved assembly process requiring the expensive and burdensome steps of stamping, orienting, stacking and fastening of the core laminations. Yet another drawback is that the assembly technique results in inefficient magnetic flux paths, thereby increasing the required size of the contactors. A further drawback is that the core lamination material used in the assembly technique is relatively thick because the laminations are stamped, oriented, stacked, riveted and in general handled as individual components. The thicker lamination material, in turn, increases eddy currents and bending stresses, resulting in a decrease in magnetic core permeability. Another drawback is that stamping methods used in the assembly technique produce a high percentage of scrap, which results in a waste of expensive iron core material. In addition, these stamping methods produce stresses in the iron material which degrade the permeability of the core.
A need therefore exists for a method for manufacturing an electrical switching contactor which overcomes the aforementioned drawbacks associated with existing manufacturing techniques.